Industrial X-ray inspection apparatuses known in the art may use image information obtained through X-ray imaging to detect defects or faults in industrial products. Such X-ray inspection apparatuses can inspect parts of a workpiece not easily viewable in the appearance or the internal state of a workpiece in a nondestructive manner, and are used in, for example, inspecting the state of solder joints on components mounted on a surface mounting board.
Imaging techniques used in X-ray inspection are mainly 2D imaging or 3D imaging. In 2D imaging, X-rays are applied to an inspection workpiece in one direction, and the resulting transmission image is obtained as 2D image information. In 3D imaging, multiple transmission images are captured by changing the direction in which X-rays are applied. Using the obtained images, 3D image information for an inspection workpiece, such as 3D volume data or a tomographic image at a given section of the object, is obtained. Computed tomography (CT) and tomosynthesis are typically known as such 3D imaging techniques. The inspection using 2D image information obtained from 2D images is herein referred to as 2D inspection. The inspection using 3D image information obtained from 3D images is referred to as 3D inspection.
As shown in FIG. 16A, a ball grid array (BGA) component may have, for example, a defective state in which a gap forms between a solder ball 162 on a component 160 and a solder paste piece 163 on a circuit board 161 (open), or a defective state in which a solder ball 162 is not fused with a solder paste piece 163 (unfused or head in pillow). However, as shown in FIG. 16B, solder balls 162 and solder paste pieces 163 cannot be easily distinguished in the transmission image obtained through 2D imaging. Distinguishing components in defective states from non-defective components is thus difficult. As a result, 2D inspection can allow such defective components to pass the inspection due to false negatives, or can lower the first pass yield due to false positives. For such defects that are difficult to detect by 2D inspection, 3D inspection may be used. For example, Patent Literature 1 describes a technique for inspecting solder balls in a BGA component with high accuracy using tomographic images obtained through tomosynthesis.